[Bone-supported rapid maxillary expansion with an implant-borne Hyrax screw: the Dresden Distractor]

Rapid palatal expansion is indicated in the orthopedic treatment of transverse maxillary deficiency for correction of severe crossbite. The fixation of the appliance at the teeth crowns leads to more tipping at the two halves of the maxilla than bodily transverse movement. Additional resorptions at the buccal cortical bone with fenestrations and gingival retraction were observed. The aim of the present study was focused on the improvement of bodily movement and optimization of the surgical osteotomy (Glassman's technique) in adult patients with application of the Dresden Distractor (DD). In 15 patients, the new method involving minimized surgical intervention and direct fixation of the hyrax screw by one implant and one bone screw was tested. The implants were loaded directly by activation of the screw two times per day. CT scans were taken before and six month after insertion of the DD. In the horizontal and the vertical planes there was a V-shaped opening of the suture in anterior, respective cranial direction, corroborating previous studies. Dental arch showed this V-shape as well, indicating tooth protection. If forces are transferred via teeth the progressive increase of skeletal resistance in anterior to posterior direction lead to dental tipping. DD is a suitable minimal invasive tooth-independent bone-borne expansion method, protecting teeth and causing skeletal as well as dental effect with 10 degree less tipping and as a precondition for stable post surgical occlusion.